Digital communications, which may, for example, comprise data, voice or video signals may be carried in optical fibers. It can be desirable to interconnect optical fibers in different ways.
Optical cross-connect switches include a first group of one or more fibers on a first “side” of the switch and a second group comprising a plurality of fibers on a second “side” of the switch. The first and second “sides” of a switch relate to optical signal transmission pathways and not to a spatial arrangement. Such switches permit a fiber of the first group of fibers to be optically connected with a selected one of the fibers of the second group.
Optical cross-connect switches typically have control systems which identify two fibers that are to be optically interconnected, and align the fibers to provide an optical connection.
U.S. Pat. No. 5,206,497 discloses an optical cross-connect switch which employs a “one-sided” control system for targeting and alignment. This alignment control system attempts to direct an optical communication signal to a selected target position based on known device geometry and pre-calibrated target positions.
U.S. Pat. No. 6,005,998 discloses a switch comprising two arrays of light beam collimators. The switch comprises two motors with associated encoders to track their positions. The motors tilt a collimating lens on a transmission side of the switch, to direct a beam of a transmission fiber to a pre-calibrated target position on a receiving side of the switch. On the receiving side of the switch, two additional motors control the angle of a similar collimating lens to insert the communication signal into a selected receiving fiber.
U.S. Pat. No. 5,524,153, discloses a switch having a plurality of optical fibers, each housed in a switching unit. LED's are interspersed with the fibers. A control system can identify target fiber within the array of switching units by lighting LED's in a particular pattern to identify the fiber that is to be targeted for connection.
U.S. Pat. Nos. 6,097,858; 6,097,860; and 6,101,299, disclose a switch in which each of a plurality of fibers is housed in a switching unit. Each switching unit is associated with a number of LED's. The LED's emit control signals having a different wavelength from the communication signals. The control signals are used by a control system to make connections between desired pairs of optical fibers.
Prior art optical switches have various disadvantages including, undesirable complexity, undesirable size, undesirably slow operation, and interference between control signals and communication signals. There remains a need for optical cross-connect switches which avoid or at least reduce some of these problems.